Hibiscus plant named &#39;DUP-CDK&#39;

ABSTRACT

A new and distinct cultivar of  hibiscus  plant named ‘DUP-CDK’, characterized by glossy, dark green leaves, upright growth, and a very large flower characterized by a very large dark red eye which extends approximately one third of the petal length, the eye sharply margined with a body zone which grades evenly from light purplish pink, through peach pink, to peach at the petal edge.

Latin name of the genus and species: Hibiscus rosa-sinensis.

Variety denomination: ‘DUP-CDK’.

BACKGROUND OF THE INVENTION

The present invention relates to a new and distinct cultivar of hibiscus, botanically known as Hibiscus rosa-sinensis and hereinafter referred to by the cultivar name ‘DUP-CDK.’

Hibiscus has been the subject of human admiration for centuries. While the ancestry of present rosa-sinensis hybrids is not precisely known, today's hybrids are thought to be the products of interspecific crosses involving Hawaiian, Polynesian and Asian species, among others, some of which may no longer be found in the wild, if they are to be found at all. It is thought that the first hibiscus identified as a rosa-sinensis was a double red form of uncertain origin found in cultivation in China, India and Polynesia, to be later introduced to Hawaii from Polynesia. It is known to have been grown in Europe during the Victorian era. Eventually, it was introduced to the continental United States where it was cultivated outdoors in the Deep South as well as in regions having subtropical or Mediterranean climates (Florida and Southern California, respectively). Indoor cultivation took place in the temperate regions of the U.S. It is speculated that the original rosa-sinensis is actually a species hybrid, possibly naturally arising, involving two or more species. Regardless, present day hybrids are descended from the original double form, and are thought to include in their ancestry Hibiscus liliiflorus, H. arnottianus, H. schizopetalus, as well as other species, particularly those native to Hawaii.

Today, after decades of extensive hybridization, the moniker “rosa-sinensis” almost certainly denotes complex interspecific hybrids. Such hybrids are usually far removed from their species ancestors in form and color. Flowers characterized by spectacular size, color intensity and, in the last several decades, ringed and spotted patterns have been produced by U.S. hybridizers in Louisiana, Florida, Hawaii, Texas and elsewhere. Other hotbeds of hibiscus-breeding activity include Australia, and more recently, Tahiti. Today's flowers are removed from their species ancestors to such an extent that it is almost impossible to unravel the species component contributions which comprise a modem hybrid hibiscus.

However, in the past, despite the fact that hybridization was giving rise to flowers of spectacular size and color intensity, very few if any early hybrids attracted the attention of large scale commercial propagators. While the flowers were truly some of the most impressive in the entire plant world, hybridizers had been selecting predominantly for bloom characteristics. As a result, many of these spectacular hybrids were weak plants which, even with the best care, were short-lived and difficult to grow. The occasional production of a spectacular bloom was enough to keep the interest of those truly dedicated to growing something rare and special, and thus new hybrids continued to be produced by hobbyists with abundant passion and small amounts of greenhouse space. As a result, more breathtaking varieties were produced each year, to be distributed via grafting among dedicated hobbyists, only to die out within a time span of 10 or 15 years. It should be noted that the majority of the varieties introduced in the 1960's, 70's and even many from the 1980's and 90's are likely to be lost to cultivation, if they are not already.

Progress toward the development of a plant which an average gardener could easily grow and enjoy was slow to non-existent. Many varieties were difficult to root from cuttings, and even if they did root, many varieties, when grown on their own roots, were extremely susceptible to fungal and bacterial root rots. Some grew acceptably only as grafted plants. However, grafted plants suffer from a serious disadvantage in that the quality of the graft generally determines the quality of the plant, making the production of uniformly vigorous plants a difficult task. Furthermore, after several years, it is common for grafted plants to develop stresses at the graft union due to the unequal growth rates of the rootstock and the scion. Such stresses can eventually lead to loss of vigor and death of the plant. Moreover, grafting does not completely cure the problem of root rot; surprisingly, the rootstock, when grafted to a root rot susceptible scion was generally still more likely to suffer rot than a plant of the rootstock variety. For example, a plant of “Seminole Pink,” a garden variety commonly used as a rootstock, is highly resistant to root rot. However, when Seminole Pink is used as a rootstock for “Romeo,” a modern hybrid which is prone to root rot, the grafted plant, while less susceptible than Romeo, is more susceptible than a plant of Seminole Pink.

Perhaps the most detrimental disadvantage of grafted plants is the introduction of viruses into the scion from the rootstock. Rootstock varieties are almost invariably old garden varieties which, over the years, have become infected with multiple viruses. While the performance of such vigorous garden varieties may be largely unaffected by virus infection, the hybrid scion of a grafted plant has generally been significantly less vigorous than the garden variety rootstock, and virus infection from the rootstock resulted in a weak plant. The problem only increased with successive generations of grafting, resulting in a rapid general weakening of a given variety over time.

Because many hybrids were shy bloomers at best, the extra stresses due to virus infection, grafting, low disease resistance, and the like generally gave sparse flower production, as well as a high number of deformed blooms. Furthermore, ordinary stresses such as over/under watering and mite/insect pests resulted in a high percentage of bud drop. The buds of large-flowered hybrids often take relatively long times to reach blooming stage, and it was not uncommon to wait with anticipation while a bud swelled day by day, only to be disappointed when the mature bud toppled from its pedicel on the day it was to open.

Moreover, because of hybridizer emphasis on the flower, the plant was often relatively slow growing and sparsely clothed in leaves. Such plants usually do not attract purchasers as they do not have the appearance of garden-worthy specimens.

It has been noted in the industry that a hybrid hibiscus seems to sell only when it is bearing a bloom. The practical effect of all of the above-mentioned issues on a retail outlet is as follows. A garden center will order a number of plants. Many of the plants will arrive either in bloom or up to several days away from blooming. The blooming plants will generally sell the first day. On several subsequent days, new blooms will open on the remaining plants, and some of them will sell as well. However, by the fourth or fifth day, the lack of perfect growing conditions begins to take a toll, and the plants begin to drop their most mature buds. From this point on, the plants essentially sit around until they are marked down or even until they decline to such a degree that they must be discarded.

Such characteristics left hibiscus with the reputation that, despite the mesmerizing beauty of the flowers, they were for collectors who had time to attend to the seemingly exacting requirements of the plants. As a result, while new varieties were produced by hobbyists yearly, propagation of modern hybrids on a commercial scale was generally rare. Common garden varieties (Seminole Pink, Brilliant, President, Painted Lady, Butterfly, Lagos, for example), which are easy to root, fast growing, and tolerant of a wide range of growing conditions were the only hibiscus widely available. The “exotics” were of little interest to commercial growers.

Many new varieties of hibiscus representing a vast improvement in rosa-sinensis hybrids, have been produced by an intense hybridizing program conducted by the Inventor at his commercial nursery in Plaquemine, La. The objective of the program has been to produce varieties of hibiscus which root easily under commercial rooting conditions, grow well on their own roots, maturing rapidly into well-leaved, salable plants under commercial greenhouse conditions. Further objectives are to produce hibiscus cultivars as aforementioned, having large flowers with unique and desirable flower characteristics, such as size, color intensity and pattern.

Asexual reproduction of the new hibiscus by hardwood, semi-hardwood, and terminal cuttings taken in a controlled environment in Plaquemine, La., has shown that the unique features of this new hibiscus are stable and reproduced true to type in successive generations.

SUMMARY OF THE INVENTION

The cultivar ‘DUP-CDK’ has not been observed under all possible environmental variables. The phenotype may vary somewhat with variations in environment such as temperature, light intensity, nutrient and water status without, however, any variation in genotype. For example, during cooler weather, flowers of many hibiscus cultivars may demonstrate an increased intensity in pink tones. Furthermore, as with many varieties of hibiscus, cooler weather can result in a decrease in flower diameter, and a corresponding reduction in size of sepals and pistil. Moreover, as indicated below, plant characteristics vary greatly with culture, with internode spacings often increasing in warmer weather and with higher soil fixed nitrogen content. Plants grown at higher temperatures can also exhibit a faster rate of growth. In general the plant used in the following description was grown at temperatures which never dipped below 55 F. Because the Inventor's one gallon pot plants are grown for an average time of about 5.5 to 6 months prior to sale, and the 10-inch pot plants are grown for an average time of about 7 to 8 months prior to sale, it is difficult to provide a precise temperature profile required to give the average plant measurements described in the below description. The growing period can encompass several seasons, with seasonal fluctuations in high/low temperatures as well as photo period. It is expected that the daily high temperature ranged from about 70 F. to about 95 F., and the daily low temperature, which never dipped below 55 F., ranged from about 65 F. to about 80F.

The following traits have been repeatedly observed and are determined to be the unique characteristics of ‘DUP-CDK.’ These characteristics in combination distinguish ‘DUP-CDK’ as a new and distinct cultivar.

-   -   1. Glossy, dark green leaves.     -   2. Strongly upright habit appropriate for container production         and culture.     -   3. Very freely flowering habit.     -   4. A very large flower characterized by a very large dark red         eye which extends approximately one third of the petal length,         the eye sharply margined with a body zone which grades evenly         from light purplish pink, through peach pink, to peach at the         petal edge.

BRIEF DESCRIPTION OF THE PHOTOGRAPH(S)

The accompanying colored photographs illustrate the overall appearance of the new hibiscus, showing the colors as true as it is reasonably possible to obtain in colored reproductions of this type.

The photograph on the first sheet (FIG. 1) depicts a first day flower of ‘DUP-CDK’.

The photograph on the second sheet (FIG. 2) is a view of the reverse of the bloom.

The photograph on the third sheet (FIG. 3) depicts a flower profile with calyx.

The photograph on the fourth sheet (FIG. 4) depicts one plant in a standard one-gallon nursery pot.

The photograph on the fifth sheet (FIG. 5) depicts a mature leaf.

DETAILED BOTANICAL DESCRIPTION

In the following description, color references are made to The Royal Horticultural Society Colour Chart, Edition V, except where general terms of ordinary dictionary significance are used. The following observations, measurements, and values describe plants grown in Plaquemine, La., in a standard one-gallon nursery pot. Plants used for the description were about 26 weeks old.

-   Botanical classification: Hibiscus rosa-sinensis. -   Parentage:     -   -   Female or seed parent.—unknown.         -   Male or pollen parent.—unknown. -   Propagation:     -   -   Type.—‘DUP-CDK’ has been propagated by taking hardwood,             semi-hardwood and tip cuttings, with semi-hardwood             preferred. It should be noted that many methods of asexual             propagation, such as tissue culture and other cloning             processes, can be expected to show some degree of success in             the propagation of the present cultivar. However, of the             methods tried by the Inventor, the use of semi-hardwood             cutting has given the greatest yield of commercially salable             plants. Asexual propagation has resulted in plants which             have the flower and plant characteristics of the original             ‘DUP-CDK’ plant, and thus the variety is stable. Cuttings             from ‘DUP-CDK’ generally root well under commercial             greenhouse conditions. While greenhouse conditions such as             relative humidity and other factors such as cutting age             prior to planting affect the take, it is not unusual to get             a take of almost 100%. Please note that as successive             generations of cuttings are raised, the raiser may             experience a drop in take due to the incorporation of virus,             particularly if at some point grafted plants are prepared,             and cuttings are taken from such a plant.         -   Time to initiate roots.—An average time of initiation at             approximately 22 C. is approximately six weeks, with             slightly longer times during winter at comparable             temperatures, and slightly shorter times during summer at             comparable temperatures.         -   Time to develop roots.—An average time, at approximately 22             C., of development of a root system after initiation, is             approximately six weeks, with slightly longer times during             winter at comparable temperatures, and slightly shorter             times during summer at comparable temperatures. It should be             noted that root initiation and development can be affected             by greenhouse conditions, biological stressors such as             disease organisms, as well as environmental stressors such             as low or variant relative humidity, over- and             under-watering, temperature variations or high or low             constant temperatures. Thus, rooting times can be shorter or             longer than the times given above depending on the values of             many different characteristics during the rooting process             known in the art.         -   Root description.—Fibrous and well-branched. -   Plant description:     -   -   Plant form and growth habits.—Perennial evergreen having             strongly upright growth. The growth habit is generally not             compact. As recognized by one of skill in the art,             intermodal distance can be dependent upon greenhouse             temperature/time profile, fertilizer availability profile,             and other factors.         -   Branching habit.—Moderately well-branched, developing             approximately 2-3 laterals when a single stem plant is             pinched back to a 5-inch height.         -   Plant height, soil level to top of flowers.—A salable plant             in a standard one-gallon nursery pot can be approximately 20             inches high and 12 inches wide. Please note that cultural             variables such as those mentioned under “Plant form and             growth habits,” above, among others, can cause significant             variation from the values given herein.         -   Lateral branch description.—The average branch             characteristics of a salable plant grown in a standard             one-gallon nursery pot: Average Length: Approximately 13″.             Average Diameter: Approximately 0.8 cm measured at the             transition from green to woody stem texture. Texture:             Immature: Smooth. Mature: Woody and rough. -   Mature foliage description:     -   -   Arrangement.—Alternate, single, numerous, symmetrical.         -   Length.—Approximately 12.7 cm.         -   Width.—Approximately 11.7 cm.         -   Shape.—ovate to slightly cordate.         -   Apex.—Acute.         -   Margin.—entire at base, otherwise crenate.         -   Texture.—Glabrous, rugose.         -   Color.—Young foliage, upper surface: More green than 147A;             glossy. Mature foliage, upper surface: Generally darker than             147A; glossy.         -   Petiole.—Average Length: 3.7 cm. Average Diameter: 0.4 cm.             Texture: Very fine pubescence on upper surface; lower             surface, glabrous. It should be noted that as with other             plant growth characteristics, foliage color and size can             vary with nutrient availability, greenhouse temperature, day             length, and other conditions of culture. -   Flower description:     -   -   Natural flowering season.—Year round, with number and size             reduction in extended periods of cold weather, such as             daytime temperatures of less than 60 C. Extreme heat can             slow growth and flower production.         -   Flower arrangement.—Flowers arranged singly at terminal leaf             axils. Very free-flowering, with usually four to five             developing flower buds per lateral branch, flowers generally             face outward or upward.         -   Flower appearance.—Very large single bloom. Flowers are open             for one to two days before senescence, which is often             accompanied by partial or full petal closure. Flowers             persistent.         -   Flower diameter.—‘DUP-CDK’ flowers are generally in the             range of from about 7″ to 9″ when fully open, with largest             flowers produced during warm weather (for example, day and             night time temperatures above 73 F.).         -   Flower depth.—Flower depth was measured to average             approximately 4.0 cm. Flower depth was measured after             removal of a petal and a sepal to expose the base of the             pistil. The measurement was taken on a fully opened flower             in the direction of the pistil, from the base of the ovaries             to the maximum height of the flower petal. The depth was             measured by using the point of recurvature of the petal             whorl. It should be noted that outermost whorl of hibiscus             blossoms can flatten out during the day, or increase or             decrease in curvature or degree of petal reflex during the             day, and thus variance from the foregoing value is possible.         -   Flower bud (just before showing color).—Rate of opening: 1-2             days. Rate of opening is generally faster in warmer weather.             Flower bud dimensions were measured on a bud which was             approximately one day from opening. Bud length was measured             from the tip of the bud to the abscission zone where bud and             peduncle meet. The average length of a bud which is one day             from opening is approximately 10.5 cm. Bud diameter was             measured at the widest part of the bud, an area             approximately halfway up the outside of the developing             petals. The average diameter of a bud which is one day from             opening is approximately 3.1 cm. It should be noted that bud             dimensions can vary somewhat with cultural conditions, and             variations can even be observed in buds which are at the             same stage of development. Shape: ovate, but slightly             flared.         -   Petals.—Texture: Smooth, satiny, rugose. Arrangement: The             corolla consists of five petals arranged in a whorl, having             regular partial overlap, even when the flower is fully open.             Shape of a petal: Roughly spatulate, with a rounded apex and             a truncate base. The margin of each petal is undulate and             entire, such that the margin of the flower appears to be             undulate, and the overlap is such that the flower margin             appears circular, with small indentations at the point where             the flower margin changes from one petal to the adjacent             petal. A representative petal length was measured to be             about 10.9 cm, and was taken from the base of the petal to             the farthest point on the margin opposite the base. A             representative width is 11.1 cm, and was measured             perpendicularly to the pistil at the widest point of the             petal. Petal size can vary with cultural conditions, such as             temperature, and thus the flower size and shape can vary as             well. Often, flowers which are produced at colder             temperatures are smaller and appear more fully overlapped,             giving almost a wheel-shaped appearance. When fully open,             the edges of ‘DUP-CDK’ flowers can be recurved. The color of             a warm weather flower is described below. It has been             observed that variations in temperature can effect the             stronger or weaker expression of certain pigments, changing             the balance of color, and thus variations in color intensity             and pattern can occur with temperature. Cold weather may             intensify pink coloration. It should be noted that the             colors of hibiscus are among the most changeable of all             flowers. A newly opening morning bloom generally has the             most intense coloration, but as the flower flattens out and             is exposed to the sun, many pigments begin to fade             immediately, resulting in a flower which can look like a             different variety altogether. While the flower of ‘DUP CDK’             fades very little compared to those of many other varieties,             when exposed to strong sun, the body outside the eye zone             can fade to a very light pinkish yellow. The morning colors             are described below. Color: Upper surface: A very large             flower characterized by a very large dark 53A eye zone which             extends approximately one third of the petal length, the eye             zone sharply margined with a body zone which grades evenly             from 55C, through 52D, to 29C at the petal edge. Lower             surface: 13D on overlapping edge, grading to 11C on             underlapping edge.         -   Sepals.—Unlike the petals, sepals are relatively invariant             in color. Their size can be affected by the same cultural             conditions which affect flower size. They are generally             smooth and elongated oblong with acute apices (pointed             tips). They are fused at the long edges into a cupped calyx             bearing at its brim the five pointed tips. When the petals             of the flower spread open, the five pointed tips, which are             flush with the backs of the opening petals, are forced into             a radiating five point star-shaped configuration, which can             be observed on the profile and reverse pictures. A             representative width, which is measured perpendicularly to             the long axis of the sepal at the position on the sepal at             which the oblong edges transition from fused to unfused, is             approximately 1.1 cm. A representative length, measured on             the sepal from the free point to the fused point is             approximately 2.5 cm. Color: Upper surface: Close to 146A.             Lower surface: Close to 147A.         -   Peduncle.—Length: 6.4 cm. Angle: Approximately 40 degrees             from branch. Strength: Strong, flexible. Texture: Smooth.         -   Reproductive organs.—Androecium: Stamen number:             Approximately 100. Anther shape: Crescent. Anther color:             11D. Amount of pollen: Moderate. Pollen color: 9C.             Gynoecium: Pistil number: 1. Pistil length (from base of             ovaries to top of stigma): 9.0 cm. Style length (from base             of ovaries to stigma branching point): 8.3 cm. Style             diameter, at base: 0.9 cm. Style color: Base: 53A.             Midsection: 53C. Apex:54D. Stigma number: 5. Stigma color:             32A. It should be noted that the dimensions of a hibiscus             blossom generally change not only during bud development,             but also during opening, as well as during the life of the             opened flower. For instance, upon opening, the petals             generally gain in length. Furthermore, after opening, the             pistil continues to grow in length while the anther             filaments which hold the pollen sacs increase in length, the             pollen sacs open and the stigmas separate, each at the tip             of a branched style structure. Toward the end of the flower             life, possibly due to a reduction in turgor pressure, the             pistil may shrink in length and the petals may slightly             decrease in area. Usually, the senescing petals of the             flower fold toward the pistil to some degree, in some cases,             completely enfolding it. -   Disease resistance: ‘DUP-CDK’ has not been observed to be resistant     to pathogens common in hibiscus. However, it has been observed in     the green house to have a higher resistance to root rot than that of     many existing hybrid varieties grown on their own roots. If desired,     and if the risk of virus infection is of no concern, the present     variety can be grafted onto a rootstock and be grown as a grafted     plant. 

It is claimed:
 1. A new and distinct hibiscus plant named ‘DUP-CDK’, either grafted or on its own roots, as illustrated and described. 